• Use the principles of atomic structure and/or chemical bonding to explain each of the following. In each part, your answer must include references to both substances

• a. The atomic radius of Li is larger than that of Be.

• The atomic radius of Li is larger than Be because

• Li and Be are both on the same period (row) of the periodic table.

• Since Be further to the right of the period, there are more protons in Be, so that the electrons of Be are pulled in closer than in Li.

b. The second ionization energy of K is greater than the second ionization energy of Ca.

• After K is ionized once it is isoelectronic with Ar, a noble gas.

• Noble gases are very stable compounds that like to keep their electron configurations, so that it takes an exceptionally high amount of energy to ionize an element with a noble gas electron configuration

Increasing First Ionization Energy

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• When Ca is ionized the first time, it becomes isoelectronic with K.

• Since K is on the very left of the period, it has a very low ionization energy, far lower than that of the second ionization energy of K (which is isoelectronic with Ar, which has a very high ionization energy) .

• c. The carbon-to-carbon bond energy in C2H4 is greater than it is in C2H6.

• The carbon to carbon bonds in C2H4 are greater because C2H6 has double bonds whereas C2H6 has only single bonds

• d. The boiling point of Cl2 is lower than the boiling point of Br2

• Both Cl2 and Br2 have London dispersion forces, however, Cl2 is lighter than Br2, so that it experiences less dispersion forces and therefore boils at a lower temperature.